(1) Field of the Invention
The present invention relates to digital portable telephone devices in which frequency-division multiple access (FDMA) is carried out by using a signal within either one of an analog frequency band and a digital frequency band.
Marketing of digital portable telephones by new business ventures in Japan has started in April 1995, and low-cost digital portable telephones have come to be available to the users. The number of digital portable telephone subscribers is remarkably increasing.
Because of the rapid growth in demand for portable telephone services, the available transmission capacity in some areas is frequently saturated, eroding customer satisfaction. Currently, there is a need for increasing the capacity of the available channels in order to reduce the occurrences of busy conditions in transmission lines.
As one of the measures for satisfying the need, introduction of a dual-rate standard, in addition to the existing full-rate standard, started in December 1995. When a dual-rate system is placed in operation, switched operations of a full-rate codec and a half-rate codec are performed.
A further increase in the number of portable telephone subscribers in the future is expected. New digital portable telephone systems which enable the capacity of the available channels to be increased by allocating the frequency bands for the existing analog systems to the frequency bands for the digital systems will be introduced to practical use.
(2) Description of the Related Art
FIG. 1A shows analog receiving/transmitting frequency bands used by existing digital portable telephone devices, and FIG. 1B shows digital receiving/transmitting frequency bands used by the existing digital band portable telephone devices.
As shown in FIG. 1A, the existing digital portable telephone devices use receiving frequencies of 870 MHz-885 MHz (which will be called analog receiving frequencies) and transmitting frequencies of 925 MHz-940 MHz (which will be called analog transmitting frequencies). The difference between the receiving frequencies and the transmitting frequencies for the existing digital portable telephone devices is about 55 MHz.
As shown in FIG. 1B, the existing digital portable telephone devices use receiving frequencies of 810 MHz-826 MHz (which will be called digital receiving frequencies) and transmitting frequencies of 940 MHz-956 MHz (which will be called digital transmitting frequencies). The difference between the receiving frequencies and the transmitting frequencies for the existing digital portable telephone devices is about 130 MHz.
FIG. 2 shows a basic configuration of a conventional digital portable telephone device which uses both the analog and the digital frequency bands. As shown in FIG. 2, the conventional digital portable telephone device generally has a receiver section and a transmitter section.
The receiver section comprises a receiving antenna (ANT0), a switch (SW1), a switch (SW3), a digital-band radio-frequency receiver (RX1) unit 12, an analog-band radio-frequency receiver (RX2) unit 14, a switch (SW5), an intermediate-frequency (IF) unit 16, and a demodulator (DEM) unit 18. The switch SW1 is provided to select a diversity mode in which a switching between the receiving antenna ANT0 and a transmitting antenna (ANT1) is performed. The switch SW3 is provided to select one of an input of the RX1 unit 12 and an input of the RX2 unit 14 for the receiver section. The switch SW5 is provided to connect one of an output of the RX1 unit 12 and the RX2 unit 14 to an input of the IF unit 16.
In order to cover the analog and digital receiving bands, the digital-band RX1 unit 12 and the analog-band RX2 unit 14 are separately provided in the receiver section, and the IF unit 16 is provided in common for the RX1 unit 12 and the RX2 unit 14.
In the conventional digital portable telephone device of FIG. 2, a control unit, including a time division multiple access (TDMA) unit 20, a coder/decoder (CODEC) unit 22 and an audio-frequency amplifier (AUDIO) unit 24, is provided in common for the receiver section and the transmitter section. An input/output interface (I/O) unit 34 is connected to the TDMA unit 20, the CODEC unit 22 and the AUDIO unit 24 in the control unit. Further, in the control unit, a central processing unit (CPU) 30 and memory devices 32 (ROM, RAM) are provided. A speaker (SPK) 26 is connected to the AUDIO unit 24 and constitutes an element of the receiver section. A microphone (MIC) 28 is connected to the AUDIO unit 24 and constitutes an element of the transmitter section.
Further, the transmitter section of the conventional digital portable telephone device comprises a transmitting antenna (ANT1), a switch (SW2), a switch (SW4), a radio-frequency modulator (RF MOD1) unit 38, a digital-band transmitter (PA1) unit 40, a radio-frequency modulator (RF MOD2) unit 42, an analog-band transmitter (PA2) unit 44, and a base-band modulator (MOD BB) unit 36. The switch SW2 is provided to select one of the receiver section and the transmitter section. The switch SW4 is provided to connect one of an output of the PA1 unit 40 and an output of the PA2 unit 44 to the transmitting antenna ANT1.
In order to cover the analog and digital transmitting bands, the digital-band PA1 unit 40 (including the RF MOD1 unit 38) and the analog-band PA2 unit 44 (including the RF MOD2 unit 42) are separately provided in the transmitter section, and the MOD BB unit 36 is provided in common for the PA1 unit 40 and the PA2 unit 44.
In the conventional digital portable telephone device of FIG. 2, a voice signal received at the receiving antenna xe2x80x9cANT0xe2x80x9d is delivered to either one of the digital-band RX1 unit 12 and the analog-band RX2 unit 14 via the switches SW1 and SW3. The signal from one of the RX1 unit 12 and the RX2 unit 14 is, delivered to the TDMA unit 20 through the switch SW5, the IF unit 16 and the DEM unit 18.
The TDMA unit 20 generates a reproduction signal by using a demodulated signal from the DEM unit 18, and separates a demultiplexed signal from the reproduction signal. The CODEC unit 22 converts the demultiplexed signal from the TDMA unit 20 into a decoded signal. The decoded signal from the CODEC unit 22 is amplified by the AUDIO unit 24. The speaker 26 is driven in accordance with the amplified signal from the AUDIO unit 24.
On the other hand, a voice signal supplied from the microphone 28 is processed in a reverse manner. A digital signal processed by the TDMA unit 20 in response to the voice signal is sent to the MOD BB 36. A modulated signal from the MOD BB unit 36 is passed through one of the digital-band transmitter (the RF MOD1 unit 38 and the PA1 unit 40) and the analog-band transmitter (the RF MOD2 unit 42 and the PA2 unit 44). A transmitting signal from one of the digital-band transmitter and the analog-band transmitter is sent to the transmitting antenna ANT1 via the switches SW4 and SW2. This signal is transmitted from the transmitting antenna ANT1.
Next, FIG. 3 shows a detailed structure of the conventional digital portable telephone device. A description will now be given of an operation of the receiver section of the conventional digital portable telephone device with reference to FIG. 3.
As shown in FIG. 3, in the conventional digital portable telephone device, a switch SW61 is provided to select the diversity mode, a switch SW62 is provided to select one of the receiver section and the transmitter section, a switch SW63 is provided to select one of the digital-band receiver and the analog-band receiver, and a switch SW64 is provided to connect one of the digital-band transmitter and the analog-band transmitter to the transmitting antenna ANT1.
When a radio-frequency signal within the digital receiving frequencies of 810 MHz-826 MHz is received at the receiving antenna ANT0, the received signal is sent to a band-pass filter (BPF) 601 via the switches SW61 and SW63. The signal passed through the BPF 601 is amplified by a low-noise amplifier (LNA) 602 and it is passed through a band-pass filter (BPF) 603. The radio-frequency signal passed through the BPF 603 is sent to a first input of a first mixer (MIX) 604.
In the conventional digital portable telephone device, a digital-band local signal generating section and an analog-band local signal generating section are provided (which will be described later). The digital-band local signal generating section supplies a first local signal (940 MHz-956 MHz) to a second input of the first mixer 604 via a hybrid (H) unit 622. The signal at the first input of the first mixer 604 is converted into a first intermediate-frequency signal (130 MHz) by using the first local signal, and the first intermediate-frequency signal is delivered to a first input of a second mixer (MIX2) 606 via a band-pass filter (BPF) 605.
The digital-band local signal generating section supplies also a second local signal (129.55 MHz) to a second input of the second mixer 606 in the digital-band receiver section. The first intermediate-frequency signal at the first input of the second mixer 606 is converted into a second intermediate-frequency signal (450 kHz) by using the second local signal. The second intermediate-frequency signal is delivered to an intermediate-frequency amplifier (IF AMP) 608 via a switch SW65 and a band-pass filter (BPF) 607. The amplified signal (IF) from the IF AMP 608 is sent to the control unit. The IF AMP 608 sends also a reception-level signal (RSSI) to the control unit.
On the other hand, when a radio-frequency signal within the analog receiving band of 870 MHz-885 MHz is received at the receiving antenna ANT0, the received signal is passed through the switches SW61 and SW63 and it is sent to a band-pass filter (BPF) 609. The radio-frequency signal passed through the BPF 609 is amplified by a low-noise amplifier (LNA) 610 and it is passed through a band-pass filter (BPF) 611. The radio-frequency signal passed through the BPF 611 is sent to a first input of a first mixer (MIX) 612.
The analog-band local signal generating section supplies a first local signal (925 MHz-940 MHz) to a second input of the first mixer 612 via a hybrid (H) unit 632. The signal at the first input of the first mixer 612 is converted into a first intermediate-frequency signal (55 MHz) by using the first local signal, and the first intermediate-frequency signal is delivered to a first input of a second mixer (MIX2) 614 through a band-pass filter (BPF) 613.
The analog-band local signal generating section supplies also a second local signal (54.55 MHz) to a second input of the second mixer 614. The first intermediate-frequency signal at the first input of the second mixer 614 is converted into a second intermediate-frequency signal (450 kHz) by using the second local signal. The second intermediate-frequency signal is delivered to the intermediate-frequency amplifier (IF AMP) 608 via the switch SW65 and the band-pass filter 607. The amplified signal (IF) from the IF AMP 608 is sent to the control unit.
As described above, in the conventional digital portable telephone device, the digital-band local signal generating section includes a phase-locked loop (PLL) 619, a low-pass filter (LPF) 620, and a voltage-controlled oscillator (VCO) 621. These elements generate the digital-band first local signal (940 MHz-956 MHz) by using an output signal of a reference oscillator (TCXO) 618. The reference oscillator 618 is connected to the PLL 619. The first local signal is supplied from the hybrid unit 622 to either the first mixer 604 in the digital-band receiver section or a radio-frequency modulator (RF MOD) unit 637 in the digital-band transmitter section.
The digital-band local signal generating section further includes a phase-locked loop (PLL) 623, a low-pass filter (LPF) 624, and a voltage-controlled oscillator (VCO) 625. These elements generate the digital-band second local signal (129.55 MHz) by using the output signal of the reference oscillator 618. This second local signal is supplied to the second mixer 606 in the digital-band receiver section.
The analog-band local signal generating section includes a phase-locked loop (PLL) 629, a low-pass filter (LPF) 630, and a voltage-controlled oscillator (VCO) 631. These elements generate the analog-band first local signal (925 MHz-940 MHz) by using the output signal of the reference oscillator 618. The first local signal is supplied from the hybrid unit 632 to either the first mixer 612 in the analog-band receiver section or a radio-frequency modulator (RF MOD) unit 644 in the analog-band transmitter section.
The analog-band local signal generating section further includes a phase-locked loop (PLL) 633, a low-pass filter (LPF) 634, and a voltage-controlled oscillator (VCO) 635. These elements generate the analog-band second local signal (54.55 MHz) by using the output signal of the reference oscillator 618. The second local signal is supplied to the second mixer 614 in the analog-band receiver section.
Next, a description will be given of an operation of the transmitter section of the conventional digital portable telephone device with reference to FIG. 3.
The first local signal (940 MHz-956 MHz) from the digital-band local signal generating section is supplied from the hybrid unit 622 to the RF MOD unit 637 in the digital-band transmitter section. The RF MOD unit 637 generates a xcfx80/4-shifted QPSK modulation signal by using the first local signal, and this modulation signal is passed through a band-pass filter (BPF) 638, a driver circuit (PA DRV) 639, a power amplifier (PA) 640, a coupler (CP) 641, an isolator (ISO) 642, and a low-pass filter (LPF) 651. The amplified signal passed through the LPF 651 is supplied to the transmitting antenna ANT1 via the switches SW64 and SW62, and it is transmitted from the transmitting antenna ANT1.
Control of transmission power related to the digital-band transmitter section is carried out by the driver circuit 639, the power amplifier 640, the coupler 641, a power amplifier controller (PA CONT) 643, and the control unit.
The second local signal (925 MHz-940 MHz) from the analog-band local signal generating section is supplied from the hybrid unit 632 to the RF MOD unit 644 in the analog-band transmitter section. The RF MOD unit 644 generates a xcfx80/4-shifted QPSK modulation signal from the second local signal, and this modulation signal is passed through a band-pass filter (BPF) 645, a driver circuit (PA DRV) 646, a power amplifier (PA) 647, a coupler (CP) 649, an isolator (ISO) 650, and a low-pass filter (LPF) 652. The amplified signal passed through the LPF 652 is supplied to the transmitting antenna ANT1 via the switches SW64 and SW62, and it is transmitted.
Control of transmission power related to the analog-band transmitter section is carried out by the driver circuit 646, the power amplifier 647, the coupler 649, a power amplifier controller (PA CONT) 648, and the control unit.
As shown in FIG. 3, a flash read-only memory (FLASH ROM) is connected to the control unit. In the flash read-only memory, program code instructions for the CPU to execute a call processing procedure, a digital/analog frequency band switching procedure, and other procedures, are stored.
FIG. 4 shows a local signal generating section in the conventional digital portable telephone device. FIG. 5 shows a phase-locked loop in the local signal generating section of FIG. 4.
Next, a description will be given of an operation of the local signal generating section with reference to FIG. 4 and FIG. 5.
In the conventional digital portable telephone device, the digital-band local signal generating section and the analog-band local signal generating section generate the second local signal (129.55 MHz) and the second local signal (54.55 MHz) in the same manner. For this reason, only a phase-locked loop in the analog-band local signal generating section is shown in FIG. 5.
In the phase-locked loop (PLL) of FIG. 5, a first frequency divider (1/N1), a phase comparator (PD) and a second frequency divider (1/N2) are connected as shown. A frequency divider setting signal is externally supplied to the first frequency divider (1/N1) and the second frequency divider (1/N2). A frequency division number N1 for the first frequency divider (1/N1) is set at 256. A frequency division number N2 for the second frequency divider (1/N2) is set at 2591 when the output frequency of the PLL is 129.55 MHz. When the output frequency of the PLL is 54.55 MHz, the frequency division number N2 is set at 1091.
As shown in FIG. 5, an output signal (12.8 MHz) of the reference oscillator (TCXO) 618 is converted into a reference signal (50 kHz) by the first frequency divider (1/N1) where N1=256. The reference signal (50 kHz) from the first frequency divider (1/N1) is supplied to a first input of the phase comparator (PD).
A signal (54.55 MHz) at an output of a voltage-controlled oscillator (VCO2) is converted into a signal (50 kHz) by the second frequency divider (1/N2) where N2=1091. The signal (50 kHz) output from the second frequency divider (1/N2) is supplied to a second input of the phase comparator (PD). The phase comparator (PD) performs a frequency comparison between the reference signal at the first input and the signal at the second input, and outputs a signal indicating the difference in frequency between the output signal of the first frequency divider (1/N1) and the output signal of the second frequency divider (1/N2). The resulting signal from the phase comparator (PD) is passed through a low-pass filter (LPF2) and it is supplied to the voltage-controlled oscillator (VCO2). Therefore, an oscillation frequency at the output of the voltage-controlled oscillator (VCO2) is controlled so as to minimize the frequency difference indicated by the output signal of the phase comparator (PD).
In the local signal generating section of FIG. 4, a duplicate structure of digital-band and analog-band phase-locked loops (PLL1, PLL2) as in the phase-locked loop of FIG. 5 is connected as shown. A digital/analog band switching signal is externally supplied to each of a switch SW67, the phase-locked loop PLL1 and the phase-locked loop PLL2. The switch SW67 is actuated in response to the digital/analog band switching signal, so as to select one of the output signal (129.55 MHz) of the voltage-controlled oscillator (VCO1) and the output signal (54.55 MHz) of the voltage-controlled oscillator (VCO2). Therefore, the local signal generating section generates the second local signal in synchronism with the output of the reference oscillator 618.
As described above, to cover the analog receiving/transmitting frequency bands and the digital receiving/transmitting frequency bands, it is necessary for the conventional digital portable telephone device to have a duplicate structure of digital-band and analog-band transmitter circuits, a duplicate structure of digital-band and analog-band receiver circuits, and a duplicate structure of digital-band and analog-band local signal generating sections. The conventional digital portable telephone device has to have a complicated configuration and a bulky size, and it is difficult to reduce the cost while the limited frequency bands are covered.
An object of the present invention is to provide an improved digital portable telephone device in which the above-mentioned problems are eliminated.
Another object of the present invention is to provide a digital portable telephone device which provides a simple configuration capable of covering the analog and digital transmitting/receiving bands and avoiding a redundant structure having the digital-band and analog-band transmitter sections, receiver sections and local signal generating sections as in the conventional device.
The above-mentioned objects of the present invention are achieved by a digital portable telephone device comprising: a receiver section which receives a signal within either one of an analog receiving frequency band and a digital receiving frequency band, wherein a received signal is converted into one of a digital-band first intermediate-frequency signal and an analog-band first intermediate-frequency signal by using a first local signal; a transmitter section which transmits a signal within either one of an analog transmitting frequency band and a digital transmitting frequency band, wherein a modulation signal is generated by using the first local signal; and a radio-frequency local signal generating section which generates the first local signal within either one of a digital local signal frequency band and an analog local signal frequency band, and supplies the first local signal to either one of the receiver section and the transmitter section.
The above-mentioned objects of the present invention are achieved by a digital portable telephone device comprising: a receiver section which receives a signal within one of an analog receiving frequency band and a digital receiving frequency band, wherein a received signal is converted into a first intermediate-frequency signal that is common for both the analog receiving frequency band and the digital receiving frequency band, by using a first local signal; a transmitter section which transmits a signal within one of an analog transmitting frequency band and a digital transmitting frequency band, wherein a modulation signal is generated by using the first local signal; and a radio-frequency local signal generating section which generates the first local signal within one of a digital local signal frequency band and an analog local signal frequency band, and supplies the first local signal to one of the receiver section and the transmitter section, wherein a frequency of the first local signal within each of the digital local signal frequency band and the analog local signal frequency band is directly produced from oscillation frequencies of less than three voltage-controlled oscillators.
The above-mentioned objects of the present invention are achieved by a digital portable telephone device comprising: a receiver section which receives a signal within one of an analog receiving frequency band and a digital receiving frequency band, wherein a received signal is converted into a first intermediate-frequency signal that is common for both the analog receiving frequency band and the digital receiving frequency band, by using a first local signal; a transmitter section which transmits a signal within one of an analog transmitting frequency band and a digital transmitting frequency band, wherein a modulation signal is generated by using the first local signal; and a radio-frequency local signal generating section which generates the first local signal within one of a digital local signal frequency band and an analog local signal frequency band, and supplies the first local signal to one of the receiver section and the transmitter section, wherein a frequency of the first local signal within each of the digital local signal frequency band and the analog local signal frequency band is produced from oscillation frequencies of less than four voltage-controlled oscillators by using a heterodyne method.
The digital portable telephone device of the present invention is effective in providing a simple configuration for each of the transmitter section, the receiver section and the local signal generating section while covering the analog and digital transmitting/receiving bands. It is possible for the digital portable telephone device of the present invention to avoid a redundant structure having the digital-band and analog-band transmitter sections, receiver sections and local signal generating sections as in the conventional device but to achieve the same functions as the conventional device at low cost.